Java vs TypeScript

• A Hello world needs package, class, static method and the actual printf.
• Reading a line from input requires instatiating 5 objects in the right order.
• Exceptions are everywhere, particularly since all values are nullable.
• Java has a getter/setter culture, but without native syntax support.
• portable Java code lacks anonymous functions, and continues to lack good support for partial application, compensating instead with verbose design patterns, kludges like anonymous inner classes, or just inline code.
• It is statically typed without type inference, with a culture that promotes long class names.
• Poor support for sum-types and pattern matching leads to overuse of inheritance for dynamic dispatch and chains of nested conditionals

Especially for beginners, this can make reading Java code feel overwhelming; most Java courses tell students to simply copy, paste, and ignore a significant percentage of the code until they've learned enough to understand what it means.

For experienced programmers, this makes Java feel tedious, especially without an IDE, and actively discourages some solutions and some forms of abstraction.

Some features in Java can be quite confusing for beginners.

Encapsulation is needlessly obfuscated with a confusing access control model. As an example, the "protected" keyword not only grants access to child classes, but to the entire package. Since small programs are written as one package, it becomes functionally equivalent to "public".

In OOP, everything is supposed to be an object, but, in Java, primitive types such as integers, booleans and characters are not, and must be handled as special cases.

Java continues to lack many high-level features, and, particularly prior to Java 7, compensated by adding confusing Java-only features, such as anonymous subclasses. Some example code is unreadable without knowing a special-case feature, libraries differ in style based on when they were released or what platform they target(e.g., Android vs. Desktop), and some solutions just aren't available on some platforms.

Overly focuses on class-based OOP to the detriment of programmer freedom or alternative paradigms that are better for various problems. Traps programmers into an always use class-based OOP mindset.

Type erasure means it doesn't even exist at runtime. The whole generics system is confusing for beginners.

Too far from the machine hardware.

I've been developing in Java for 20 years and I love this language, I've never used a better designed one over the last 30+ years. However, starting with version 6, the number of really useful features in each release has steadily decreased. There is now too much marketing in Java's evolution and too few concern about developers' needs (the functionalities of the applications we develop haven't changed and enterprise application architecture is much simpler than 20 years ago). I'm deeply sad to say that today, learning Python is a much wiser choice.

Java is a garbage collected language and it does not force programmers to think about memory allocation and management for their programs. This is fine most of the time. However, it may cause some difficulties in adjusting to a non-GC language (such as C for example), where memory management needs to be done manually. But if good coding practices and habits are followed, this shouldn't be much of a problem.

It's just barely good enough to make decent IDEs, but it's not at the level of Idris or even Haskell. For large enterprise projects, the IDE support is important, but the static typing in Java just gets in the way for the smaller projects beginners would start with.

Python is duck typed and this makes small programs easy to develop quickly, but the price is that you have to write unit tests to avoid breaking larger programs. In contrast, you can be reasonably certain that a program that actually compiles in Idris does what you want, because assertions are built into the powerful type system. Java can't make that claim and still requires unit tests. Java has the worst of both worlds because of its poor static type system.

The type system gets in your way more than it helps. Heavy IDE support is absolutely required for reasonable productivity. This means beginners have to learn not just the language, but eventually a complex, heavyweight IDE too.

Java evolves very slowly - lambda expressions weren't available until Java 8 (which is not available on Android), and despite getters/setters being a long-time convention, the language still doesn't have native accessor syntax (a la C#'s properties). It's unlikely newer, popular features like list comprehensions or disjoint union types will be available anytime soon. While not strictly required for novice programmers, these make problems more complicated and tedious than they need to be - for example, when a simple local function would do, (portable) Java demands anonymous inner classes, an interface and a class, or worse, no abstraction at all.

Since C# came later, it could avoid the blatant mistakes made in Java.

Java utilizes principles that primarily organize code into "classes" as the central concept, instead of more familiar organizational methods.

Checked exceptions add significantly to the cognitive load of the beginner. The more rules unrelated to the actual task that you pile onto the beginner, the slower he gets. Exponentially. And for what? Sure, they look good on paper, but checked exceptions are useless in the real world. They don't scale.

When you're calling APIs five levels deep and your method's throws clause balloons to 80 exceptions you might see, it gets kind of ridiculous. So you just say throws Exception, which defeats the whole feature, but is more pointless boilerplate in an already tediously verbose language.

Or worse, while developing you can't be bothered and just catch{} and silently swallow them all. Then you forget about it. Now you don't even have exceptions. The cure is worse than the disease!

So the wiser Java programmers will wrap all checked exceptions into a runtime exception, effectively making exceptions unchecked. That's at the cost of more boilerplate, but it's the lesser of evils. Unfortunately, Java doesn't even have macros to do this part for you. Maybe your IDE can write code templates for you, but that doesn't make it any easier to read.

Presents some advantages compared to Javascript, but because it is designed to be a superset of Javascript, it means all the bad parts of Javascript are still present.

You have to use compiler flags to make sure it catches flaws like usage of implicit any, etc.

The default type when declaring and using a variable is any. For example, the following should break but does not:

function add(a:number) { return a + 1 }
function addAB(a, b) {return add(a) + b}

addAB("this should break but doesn't :(", 100)

In order to avoid this, you have to declare type signatures for every variable or parameter or set the flag --noImplicityAny when running the compiler.

Even in cases were there is no ambiguity, you still have to use "this.fieldName" instead of just "fieldName".

Typescript compiler does not remove dead code from generated file(s), you have to use external tools to remove unused code after compilation. This is harder to achieve, because Typescript compiler eliminated all type information.

There is no clean way to have debug and release builds compiled from the same source, where the release version removes all debugging tools and outputs from the generated file(s).

Comparing to Elm or Rust for example, TypeScript's error messages won't say you very much. For example if you change method of interface which your class implements it won't say your class have incorrect implementation. Instead it'll show error in usage of instances of class. In some cases it can spoil hours of your work trying to figure out why your parameters are incorrect.

As consequence of not enforcing type checking.

Just compare this and this.
Typescript => 930
Dart => 2060

If you prefer a Java-like approach of partitioning your code into different packages, the module system of typescript will confuse you.